Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Giải:
\(A=1-\dfrac{5}{\sqrt{196}}-\dfrac{5}{\left(2.\sqrt{21}\right)^2}-\dfrac{\sqrt{25}}{204}-\dfrac{\left(\sqrt{5}\right)^2}{374}\)
\(\Leftrightarrow A=1-\dfrac{5}{14}-\dfrac{5}{2^2.\left(\sqrt{21}\right)^2}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=1-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=\dfrac{5}{5}-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=5\left(\dfrac{1}{5}-\dfrac{1}{14}-\dfrac{1}{84}-\dfrac{1}{204}-\dfrac{1}{374}\right)\)
\(\Leftrightarrow A=5.\dfrac{6}{55}\)
\(\Leftrightarrow A=\dfrac{6}{11}\)
Vậy giá trị của biểu thức A là \(\dfrac{6}{11}\).
Chúc bạn học tốt!
4) mấy bài kia trình bày dài lắm!! (lười ý mà ahihi)
\(\sqrt{\left(x-\sqrt{2}\right)^2}+\sqrt{\left(y+\sqrt{2}\right)^2}+|x+y+z|=0.\)
\(\Leftrightarrow|x-\sqrt{2}|+|y+\sqrt{2}|+|x+y+z|=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-\sqrt{2}=0\\y+\sqrt{2}=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\sqrt{2}\\y=-\sqrt{2}\end{cases}}}\)
Tìm z thì dễ rồi
\(M=1-\frac{5}{\sqrt{196}}-\frac{5}{\left(2\sqrt{21}\right)^2}-\frac{\sqrt{25}}{204}-\frac{\left(\sqrt{5}\right)^2}{374}\)
\(=1-\frac{5}{14}-\frac{5}{84}-\frac{5}{204}-\frac{5}{374}\left(\text{(}2\sqrt{21}\text{)}^2=2^2.21=84\right)\)
\(=1-\frac{5}{2.7}-\frac{5}{7.12}-\frac{5}{12.17}-\frac{5}{17.22}\)
\(=1-\frac{1}{2}+\frac{1}{7}-\frac{1}{7}+\frac{1}{12}-\frac{1}{12}+\frac{1}{17}-\frac{1}{17}+\frac{1}{22}\)
\(=1-\frac{1}{2}+\frac{1}{22}\)
\(=\frac{22-11+1}{22}=\frac{12}{22}=\frac{6}{11}\)
Vậy M = 6/11.
\(A=\)bn ghi lại đề nha mình lười
\(=\left(\sqrt{5+\sqrt{21}}\right)^2\left(\sqrt{14}-\sqrt{6}\right)\sqrt{5-\sqrt{21}}\)
\(=\left(\sqrt{5+\sqrt{21}}\right)\left(\sqrt{5-\sqrt{21}}\right)\left(\sqrt{5+\sqrt{21}}\right)\left(\sqrt{14}-\sqrt{6}\right)\)
\(=\left(\sqrt{\left(5^2-21\right)}\right)\left(\sqrt{5+\sqrt{21}}\right)\left(\sqrt{14}-\sqrt{6}\right)\)
\(=2.\left(\sqrt{5+\sqrt{21}}\right)\sqrt{2}.\left(\sqrt{7}-\sqrt{3}\right)\)
\(=2.\left(\sqrt{10+2\sqrt{21}}\right)\left(\sqrt{7}-\sqrt{3}\right)\)
\(=2.\left(\sqrt{7+2\sqrt{21}+3}\right) \left(\sqrt{7}-\sqrt{3}\right)\)
\(=2.\sqrt{\left(\sqrt{7}+\sqrt{3}\right)^2}\left(\sqrt{7}-\sqrt{3}\right)\)
\(=2.\left(\sqrt{7}+\sqrt{3}\right)\left(\sqrt{7}-\sqrt{3}\right)=2.\left(7-3\right)=2.4=8\)
tíck mình nha bn thanks nhìu !!!!!!!!!